Adjusting device for gas exchange valves

ABSTRACT

An method and apparatus for damping the impact and noise of the anchor plate against the pole surfaces of the electromagnets in a electromagnetically-actuated, spring biased adjusting device for gas exchange valves wherein the actuator assembly is provided with a perimeter casing member which forms an air tight enclosed gap area between the pole surfaces of the electromagnets. The anchor plate is provided with a sealing member along its perimeter edge such that a fluid cushion is formed as the anchor plate approaches a pole surface of either electromagnet. The inner wall surface of the perimeter casing is provided with overflow openings about its middle region to permit communication of fluid from the chambers in the gap on either side of the anchor plate during its mid-point of travel to reduce resistance to anchor plate movement over a majority of its operating range. One or more transverse throttle holes may be provided in the anchor plate to further control air exchange within the enclosed gap area prior to anchor plate impact.

FIELD

The invention relates generally to an improved electromagneticallyoperated adjusting device for spring-loaded reciprocating actuators indisplacement engines, such as for lifting gas exchange valves ofinternal combustion engines. More particularly, the invention relates toimprovements in reducing or dampening the impact noise associated withthe striking of a reciprocating anchor plate of the valve stem againstthe pole surface of each electromagnet as the anchor plate moves from afirst operating condition to a second operating condition correspondingto the open and closed positions of the gas exchange valve.

BACKGROUND

An example of an electromagnetically operated adjusting device for gasexchange valves of this type is shown in DE 30 24 109.

This known device discloses a gas exchange valve for an internalcombustion engine, the stem of which is joined to the valve disk and hasan anchor plate (or armature) which is alternatingly attracted to thepole surface of two opposing electromagnets upon the energizing thesolenoid associated with each electromagnet. The engagement of theanchor plate to a pole surface results in either the closed or openposition of the valve. As current flow is cut off to the contactingelectromagnet the spring system forces the anchor plate in the directionaway from the contacted pole surface where it is then attracted to theopposing pole surface by energization of the solenoid associated withthe opposing electromagnet. A disadvantage associated with adjustingdevices of this type is the noticeable impact noise of the anchor plateas it contacts each pole surface.

DE 30 24 109 teaches to dampen the impact of the moving anchor plateagainst the pole surface of an excited electromagnet by providing abiasing member, such as coil spring, to decelerate the anchor plateafter it reaches its midpoint of travel prior to impacting the affectedpole surface. This method necessitates sturdy coil springs to providesufficient damping and this means that larger electromagnets arenecessary to provide sufficient retention forces for holding the anchorplate at the open and closed positions. Thus, adequate damping resultsin undesirable increases in the size and weight of the actuator assembly

GB-A 2 137 420 discloses a similar design for anelectromagnetically-operated, spring-biased adjusting device whereindamping of the anchor plate impact is achieved by providing a skirt-likesealing member to the pole surface of each electromagnet whereby anenclosed volume of air is formed by the electromagnet pole surface andthe skirt-like sealing member just before the anchor plate impacts thepole surface. This volume of air cushions the impact as it becomescompressed and impact noise is reduced. However, since only the lastportion of anchor plate travel is controlled by this sealing affect, theability to adequately control the impact damping of a fast approachinganchor plate is limited by the cushioning effect attributed to thissmall volume which is sealed only just prior to impact.

Thus, there is a definite need in the art for an improved solenoidactuated, spring-biased, adjusting device for gas exchange valves whichhas improved means for significantly damping the impact noise associatedwith the anchor plate and which also allows for fast switching timebehavior.

THE INVENTION Objects

It is among the objects of the invention to provide an improved solenoidactuated gas exchange valve device having the properties of reducedimpact noise associated with the anchor plate as it engages the polesurface of each electromagnet;

It is another object of the invention to provide an improved actuatorassembly wherein the gap between the opposing electromagnets is sealedby a perimeter casing thus forming a cylinder for the reciprocatinganchor plate, and the anchor plate is provided with a sealing ring whichin effect divides the enclosed solenoid gap into two sealed chambers sothat a compressible volume of fluid adjacent each pole surface isprovided to reduce impact noise;

It is another object of the invention to provide an improved actuatorassembly whereby throttle holes are provided adjacent the mid-pointregion of the perimeter casing to regulate the fluid flow between bothchambers as the anchor plate compresses the air volume therein prior toengaging the affected pole surface so that fast switching time behavioris retained;

Still other objects will be evident from the following specification,drawings and claims.

DRAWINGS

FIG. 1 shows a side elevation, cross-section view of the improvedactuator adjusting device of this invention.

FIG. 2 shows a enlarged fragmentary, cross-sectional view of a second,alternate embodiment for the improved adjusting device of thisinvention.

SUMMARY

I have found that the noise associated with the impact of an anchorplate (or armature) against a pole surface of a magnet in conventionalsolenoid-actuated positioning devices for gas exchange valves can besignificantly reduced or dampened by causing a cushion of air to formbetween the anchor plate and the affected pole surface just prior toimpact. To accomplish this, an airtight casing member is provided whichseals the entire gap defined as the space between the pole surfaces ofthe opposed electromagnets wherein the anchor plate associated with thetappet of a gas exchange valve is cause to alternatingly reciprocatebetween contact with each pole surface. The enclosure area is sealedfrom the outside ambient. The anchor plate (or armature) is alsoprovided with a sealing member (such as a ring or gasket) at itsperimeter edge which contacts the inner wall of the perimeter casing ina manner such that the anchor plate divides the enclosure or gap areainto two sealed chambers whereby each chamber undergoes compressionduring the approach of the anchor plate towards its adjacent polesurface. This in turn causes a cushion of fluid to form within thatcompressed chamber to soften or dampen the anchor plate impact againstthat pole surface.

In order to ensure fast switching time behavior of the anchor platebetween each pole surface, it is desirable to minimize drag orresistance due to the compression and vacuum effects associated witheach chamber in response to the anchor plate movement. Thereforeoverflow openings are provided in the middle region of the enclosed areaalong the inner perimeter wall of the casing such that fluid may becommunicated from one chamber to the other chamber when the sealingmember of the anchor plate passes by the overflow holes. The overflowholes are sufficiently large such that the sealing member of the anchorplate permits fluid exchange between chambers over 80-90% of the centerportion of the anchor plate travel between the opposing pole surfaces.

The impact force of the anchor plate may be further controlled by theuse of one or more transverse throttle holes provided in the anchorplate which permit the exchange of fluid from a chamber area undergoingcompression (i.e., the chamber area adjacent the pole surface about tobe impacted) to the other chamber area. The overflow holes, incombination with the throttle holes, provide the desired control of theanchor plate over the entire operating range of the anchor plate suchthat fast switching time behavior is retained and the impact noise issignificantly reduced.

DETAILED DESCRIPTION OF THE BEST MODE

The following detailed description illustrates the invention by way ofexample, not by way of limitation of the principles of the invention.This description will clearly enable one skilled in the art to make anduse the invention, and describes several embodiments, adaptations,variations, alternatives and uses of the invention, including what Ipresently believe is the best mode of carrying out the invention.

FIG. 1 illustrates an isolated view of an adjusting device for a gasexchange valve of the type normally found within the engine block of aninternal combustion engine. The adjusting device comprises opposingshielded electromagnets (iron cores) 10 and 14. Each electromagnet isgenerally U shaped in cross-section to form a cup magnet and has coilsor solenoids 12 and 16 annularly installed therein. The solenoids 12 and16 are aligned parallel to the axis of the annulus coinciding with theaxis of the valve stem 32. Each electromagnet also has associatedtherewith a pole surface. Pole surface 11 is associated withelectromagnet 10 and pole surface 15 is associated with electromagnet14.

In the preferred embodiment both iron cores or electromagnets 10 and 14are cylindrical in shape and share a common axial bore 34 which isaligned with the vertical axis of the actuator assembly. An anchor plate18, being reciprocable in the vertical direction (as seen in FIG. 1) isprovided and moves back and forth between pole surfaces 11 and 15 duringoperation. The anchor plate 18 is further provided with an integrallyattached upper stem 20 which is disposed to reciprocate within the bore34 associated with upper electromagnet 10. The anchor plate alsoincludes a lower stem 30 which is disposed to reciprocate within thebore 34 associated with electromagnet 14 and presses against a stampmember or tappet 32 which forms the shaft of a gas exchange valve (valvedisc not illustrated).

A spring system is used to accelerate the anchor plate 18 from thecontact with a first pole surface of a de-energized electromagnet to theopposing pole surface of an excited electromagnet. The spring systemcomprises a first upper coil spring 22 and a second lower coil spring24. Upper spring 22, being receivingly engaged within a central bore 35of upper stem 20 is stressed to move the anchor plate 18 in a directionaway from contact with pole surface 11. Magnet cover 26 serves as a topabutment for spring 22.

In the preferred mode of the invention, upper stem 20 is in the form ofa thin walled casing and may have one or more drilled holes 33 along itsside wall to achieve a mass reduction. As is seen in FIG. 1, the anchorplate 18 is being held at pole surface 11 and spring 20 is in itscompressed state. This is accomplished by the retention or holdingforces associated with energized electromagnet 10. This operatingcondition of the adjusting device corresponds to the closed position ofthe gas exchange valve.

Spring 24 functions much like a conventional valve spring for camoperated valves in internal combustion engines as it is normallystressed to move the gas exchange valve to the closed position. As isseen in FIG. 1, spring 24 is braced against abutment 28 at its lower endand the stamp portion or tappet 37 of the valve stem 32 at its upperend. The dead point or equilibrium state of the spring system occurswhen the solenoids are not activated and is in the middle between theopposing pole surfaces 11 and 15. In other words the dead point of thespring system corresponds to the middle position of anchor plate 18travel between the opposing pole surfaces 11 and 15.

A cylindrical casing 38 is provided to seal off the air gap between theopposing electromagnets. The casing 38, magnet cover 26, and abutment 28serve to affix the electromagnets 10 and 14 within the cylinder head(not shown).

Referring to FIGS. 1 and 2, the anchor plate 18 divides the enclosed gaparea between the electromagnets into two chambers, namely upper chamber50 and lower chamber 52. Fluid may be introduced into the chambers 50and 52 thus providing a damping effect for the anchor plate 18 as itapproaches a pole surface of either electromagnet due to fluidcompression in the decreasing volume of the effected chamber. Chambers50 and 52 may communicate with each other by means of one or morecontrol orifices 44 that are selectively placed along the anchor plate18. The tolerance gaps between the outer diameters of upper and lowerstems 20 and 30 and their surrounding iron cores or electromagnets 10and 14 are sufficient to ensure that no appreciable amount of fluid ispermitted to escape from the upper and lower chambers into thesetolerance gap regions. In other words, these tolerance gap areas aresubstantially air tight.

As is seen in FIG. 1, the perimeter edge of the anchor plate 18 isprovided with a sealing member 36 which forms a perimeter seal withcasing 38 and thus inhibits the flow of fluid around the perimeter edgeof the anchor plate from one chamber to another. The sealing member 36may be in the form of a sealing ring or gasket which is set in a notchedgrove 39 in the perimeter surface of the anchor plate 18.

FIG. 2 shows an alternate embodiment of the anchor plate 18 which isalso adapted to form a perimeter seal with the casing 38 wherein a nub40 is formed on the perimeter edge of the anchor plate 18 and extendsradially to sliding contact the inside perimeter wall of casing 38.

One or more throttle holes 44 (see FIG. 1) may be provided in the anchorplate 18 to permit the additional exchange of fluid between upper andlower chambers 50 and 52. If the fluid to be used is a compressiblefluid such as air, the throttle holes serve the additional purpose ofreducing vacuum effects. If the fluid to be used is non-compressible,the throttle holes serve as a control orifice for the exchange of thefluid between both chambers.

In the preferred embodiment the fluid to be used is air, but it isunderstood that oil damping may also be preferable possible since oildamping also permits lubrication of the moving parts of the actuatorassembly. When using an oil mist for lubrication, the medium in thechambers would be composed of air and oil.

As is best seen in FIG. 2, a plurality of overflow openings 42 areprovided along the inner perimeter wall of casing 38. These overflowopenings 42 allow additional fluid exchange between the chambers 50 and52 as the anchor plate 18 reciprocates past them. The overflow openings42 are, in actuality, relieved portions (recesses) along the middle areaof the inner perimeter wall of casing 38 and thus the holes are sealedto the outside, that is, the overflow openings 42 do not extend clearthrough the wall thickness of casing 38. The overflow openings 42 thuspermit an additional exchange of fluid between the upper and lowerchambers 50 and 52 over the middle portion of the anchor plate travel asthe anchor plate moves from contact with one pole surface to the other.This, in effect, reduces the resistance to the anchor plate travel overthis middle traveling region. Over the last part of the anchor platetravel just prior to impact, the fluid contained within the chamberadjacent the impacted pole surface undergoes a rapid compression sincethe additional flow of fluid between the chambers through overflowopenings 42 is cut off by the sealing member 36 (FIG. 1) or sealing edge40 (FIG. 2) as it passes by the extreme (upper or lower) edge of theoverflow openings 42.

In operation, the anchor plate 18 is moved back and forth by thealternating excitement of solenoids 12 and 16 in combination with theacceleration forces of springs 22 and 24. In each operating conditionthe anchor plate 18 is held to the pole surface 11 or 15 of anelectromagnet 10 or 14 by a retention force generated by excitation ofthe associated solenoid 12 or 16. The springs are used to accelerate theanchor plate in a direction towards the opposing pole surface upondeactivation of current flow through the contacting electromagnet. Theresistance to the motion of the anchor plate due to fluid compression inthe chamber areas 50 and 52 is small over a large part of the path ofanchor plate travel since the overflow openings 42 provide a rapidexchange of fluid over this portion of travel. After about 80-90% of thetotal travel path has been covered by the anchor plate 18, the sealingedge 36 (FIG. 1) or 40 (FIG. 2) passes the extreme perimeter edge of theoverflow openings 42 thus preventing any further fluid flow around theperimeter edge of the anchor plate 18. A small amount of fluid exchangemay still be permitted by the optional provision of the throttle holes44. The throttle holes 44 permit the fine tuning of the chambercompression rate. Thus, as the anchor plate 18 approaches a polesurface, a fluid cushion is formed which greatly dampens the impact andcontributes to noise reduction.

The invention thus achieves the desired dampening effects by selectivelycontrolling a large volume of fluid exchange from the upper chamber 50to the lower chamber 52 so that a sufficient cushion of fluid iscompressed prior to impact through the combined use of overflow openings42 and throttle holes 44. Provision for rapid fluid exchange over themajor portion of anchor plate travel insures that fast switching timebehavior of the actuator assembly is retained as the resistive affectsof compression and vacuum as produced by the moving anchor plate isminimized.

It should be understood that the anchor plate 18 may be designed withoutthrottle holes 44 without any decrease in performance. However, constantcompression of the fluid in the system may have a tendency to createleaks in the sealing member 36 or sealing edge 40 over time, and mayeven cause fluid to escape through the tolerance gaps between upper stem20 and the interior perimeter of electromagnet 10 and lower stem 30 andthe interior perimeter of electromagnet 14. Provision of throttle holes44 reduces the tendency for such compression leaks as they providecontrolled flow of compressed air between the two chambers 50 and 52.

It should be understood that various modifications within the scope ofthis invention can be made by one of ordinary skill in the art withoutdeparting from the spirit thereof. I therefore wish my invention to bedefined by the scope of the appended claims as broadly as the prior artwill permit, and in view of the specification if need be.

I claim:
 1. An improved electromagnetically operated, spring-biasedactuator assembly for gas exchange valves in internal combustion enginescomprising in operative combination:a) a first actuating solenoid and asecond actuating solenoid, said second actuating solenoid disposedspaced apart from said first actuating solenoid to define a gaptherebetween; b) means for reciprocatingly actuating a gas exchangevalve, said gas exchange valve being movable between a first, closedoperating position to a second, open operating position; c) saidreciprocating actuator means including a generally disc-shaped anchorplate having a central axis and a peripheral edge spaced radiallyoutwardly from said axis, said anchor plate disposed in said gap totravel between said actuating solenoids and selectively attractable toand guidingly reciprocated between positions of engagement with a polesurface of each of said actuating solenoids, said first actuatingsolenoid pole surface engagement position corresponding to said closedoperating position of said gas exchange valve and said second actuatingsolenoid pole surface engagement position corresponding to said openoperating position of said gas exchange valve; d) a perimeter casingsleeve member disposed surrounding said anchor plate peripheral edge andbridging said gap, said perimeter casing having a wall with an axiallength dimension sufficient to span said gap and sealingly engage atleast a portion of each of said actuating solenoids to form an enclosureabout said gap; e) said anchor plate including means for dampening theimpact of said anchor plate as it engages the pole surface of each ofsaid actuating solenoids to reduce impact noise associated with saidanchor plate impact; f) said dampening means includes a sleeve casingsealing member disposed adjacent to and in association with saidperimeter edge of said anchor plate; g) said sealing member having aperimeter edge which slidingly contacts an inner surface of saidperimeter casing sleeve wall to divide said gap enclosure into a pair ofsealed chambers when said anchor plate moves between engagement witheach of said pole surfaces, said chambers including:i) a first sealedchamber disposed adjacent said pole surface of said first actuatingsolenoid; ii) a second sealed chamber disposed adjacent said polesurface of said second actuating solenoid; and h) said sealing member isadapted to maintain a substantially airtight seal between said perimeteredge of said anchor plate and said inner wall surface of said perimetercasing sleeve so that a cushion of compressible fluid forms adjacent thepole surface of an excited actuating solenoid to reduce impact noise assaid anchor plate approaches said excited actuating solenoid.
 2. Animproved electromagnetically operated, spring-biased actuator assemblyas in claim 1 wherein said anchor plate includes means for permittingcontrolled exchange of fluid between said first and second sealedchambers.
 3. An improved electromagnetically operated, spring-biasedactuator assembly as in claim 2 wherein said controlled fluid exchangemeans is a throttle hole.
 4. An improved electromagnetically operated,spring-biased actuator assembly as in claim 1 wherein:a) said dampeningmeans includes a flange disposed adjacent a perimeter edge of saidanchor plate; b) said flange extends a radial distance sufficient topermit sliding contact with an inner surface of said perimeter casingsleeve wall to divide said enclosure into a pair of sealed chambers whensaid anchor plate moves between engagement with each of said polesurfaces, said chambers including:i) a first sealed chamber disposedadjacent said pole surface of said first actuating solenoid; ii) asecond sealed chamber disposed adjacent said pole surface of said secondactuating solenoid; and c) said sliding contact between said flange andsaid inner wall surface having a tolerance sufficient to restrict theexchange of fluid between said first and second chambers to form acushion of compressible fluid forms adjacent the pole surface of anexcited actuating solenoid to reduce impact noise as said anchor plateapproaches said excited actuating solenoid.
 5. An improvedelectromagnetically operated, spring-biased actuator assembly as inclaim 4 wherein:a) said inner surface of said perimeter casing sleevewall includes means for controlling the exchange of compressible fluidbetween said first and second sealed chambers to reduce excess pressurebuild-up and vacuum effects within each of said chambers and to maintainfast time switching behavior of said anchor plate.
 6. An improvedelectromagnetically operated, spring-biased actuator assembly as inclaim 5 wherein:a) said fluid exchange control means is a plurality ofthrough holes medially disposed in said inner wall surface of saidperimeter casing: and b) each of said through holes has a diametersufficient to permit the controlled leakage of fluid to passtherethrough over a middle range of anchor plate travel betweenengagement with each of said pole surfaces as said flange of said anchorplate moves by said through holes.
 7. An improved electromagneticallyoperated, spring-biased actuator assembly as in claim 6 wherein:a) saidfluid exchange control means is a plurality of recesses mediallydisposed in said inner surface of said perimeter casing wall; and b)said recesses provide pathways around said flange for the controlledleakage of fluid between said first and second sealed chambers over amiddle portion of said anchor plate travel between engagement with eachof said pole surfaces.